"!icase || ascii_only" is repeated twice in this if/else chain as this
series evolves. Rewrite it (and basically revert the first if
condition back to before the "grep: break down an "if" stmt..." commit).
Helped-by: Junio C Hamano <gitster@pobox.com> Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>